This invention pertains to marine systems using planctomyetes for removal of ammonia under anaerobic conditions.
Understanding the parameters necessary for optimizing biological nitrogen removal filters in recirculated aquaculture systems is an important research area in modern aquaculture. Despite their importance, there is a dearth of information about the identity and ecology of the microorganisms involved in catalyzing nitrogen (N) removal in these systems (van Rijn, 1996). Most studies on N-removing bacteria in recirculated aquaculture filters or wastewater treatment plants have focused on the nitrifying consortia belonging to the β- and α-subdivisions of the Proteobacteria, i.e. Nitrosomonas sp., Nitrobacter sp., and Nitrospira sp., that occupy aerobic biofiltration units (Princic et al., 1998; Kloep et al., 2000). For many years the general assumption has been that ammonia- and nitrite-oxidizing species were identical in marine and fresh water environments. Recent innovations in microbial ecology techniques, however, have shown that this is not the case. Using oligonucleotide probes to examine nitrifying bacterial populations associated with freshwater and marine aquaria Hovanec and Delong (1996) found that bacteria responsible for ammonia oxidation, Nitrosomonas europaea, appear to be present at high levels in seawater aquaria and at very low levels in freshwater aquaria. Other studies demonstrated that the important nitrite-oxidizing bacteria in fresh and marine environments belong to Nitrospira sp. and not to Nitrobacter sp. as was previously thought (Daims et al., 2000). Thus, while a small number of studies have begun to examine biological filtration systems used in aquaculture almost no information is available about the specific members that compose the bacterial consortia in aerobic filters and the role that they play in N-removal processes. For example, the involvement of anaerobic ammonia oxidizing (anammox) bacteria (Strous et al., 1999) in contributing to ammonia removal in aerobic biofiltration units has not been examined. The wide range of chemical and physical conditions present in these biofilters as well as the various nutrients that are available for bacterial consumption makes it likely that many key microorganisms have been ignored.
One of the main problems in exploring microbial diversity in complex environments, such as those associated with biological filters, is the fact that many of the important microorganisms cannot be cultivated by traditional methods. The availability of molecular tools, such as those used to analyze 16S ribosomal DNA (rDNA) sequences, have made it possible to explore slow growing or uncultivated bacterial species in different environments (O'Donnell and Gorres, 1999). A moving bed bioreactor (MBB) that is a component of a marine recirculated system was used to survey the bacterial community. This approach provided information about the bacterial diversity in these filters and provided some insight into the roles for different bacterial species in the inorganic nitrogen removal process. This information can be used to enhance the efficiency of these biofilters by optimizing operating conditions to induce a desirable process necessary for closing the nitrogen cycle and releasing the fixed nitrogen back to the atmosphere.
U.S. Pat. Nos. 5,078,884 and 5,259,959 by Mulder describe biological anaerobic denitirification of wastewater by bacteria. Mulder describes a system comprising bacteria for the anammox removal of ammonia from freshwater. No marine bacteria are described and the disclosed system is a freshwater system. U.S. Pat. No. 5,660,142 discloses a water purification system for either a fresh or saltwater fish culture system where ammonia is oxidized by nitrifying bacteria to nitrate and nitrate is reduced to gaseous N2 and short chain volatile fatty acids are oxidized to CO2 by anaerobic bacteria in a fluidized bed reactor. U.S. Pat. No. 5,660,142 does not disclose a system or method comprising any marine anammox bacteria.